Seismic pressure transducer assemblies adapted for marshy terrains are known and widely used. One such pressure transducer assembly comprises a rigid cylindrical perforated casing defining an inner cavity. An air-filled bag or bladder containing a pressure transducer element is mounted inside the cavity. The bag is made from a sound-transmitting material such as rubber. When the transducer assembly is submerged in shallow water or marshy ground, the water fills the cavity through the perforations of the casing. Seismic pressure waves from the liquid are transmitted to the pressure transducer through the wall of the bag and the air therein.
Such known seismic transducer assemblies have certain drawbacks chief among which are: the wall of the rubber bladder has to be relatively thin in order not to unduly attenuate the arriving seismic pressure waves. But, a thin-walled bladder is susceptible of becoming easily damaged by sharp objects piercing through the perforations of the casing. When the bladder becomes ruptured, the air therefrom escapes, water enters the inner volume of the bladder and damages the transducer element. Another serious problem with such prior art transducer assemblies is that mud enters the cavity of the casing and forms a "cake" around the bladder, thereby preventing effective acoustic coupling between the external fluid medium and the transducer element.